Abstract

We propose and show that for coupling modulated lasers (CMLs), in which the output coupler is modulated rather than the pump rate, the conventional relaxation resonance frequency limit to the laser modulation bandwidth can be circumvented. The modulation response is limited only by the coupler. Although CMLs are best suited to microcavities, as a proof-of-principle, a coupling-modulated erbium-doped fiber laser is modulated at 1 Gb/s, over 10000 times its relaxation resonance frequency.

(a) Schematic of the CM-EDFL in the experiment. (b) Output power versus coupled pump power for two of the bias coupling strengths, |κ0|2, used in this experiment. (c) Spectrum of the laser output for |κ0|2 = 0.5% showing single longitudinal mode operation. (d) The output response to a 100 μs pump modulation pulse starting at a time of 0 μs, where Ppump = 69 mW and |κ0|2 = 0.5%.

(a) Small-sinusoidal-signal response of the coupling-modulated laser (Ppump = 75 mW) and the coupler modulator for |κ0|2 = 0.5% between 30 kHz to 5 GHz. The inset of (a) shows the output intensity with 100 MHz coupling modulation. (b) A high resolution measurement of the coupling modulation response of the laser measured in (a).

(a) The envelope of the output obtained by undersampling the EDFL output with magnified views of the beginning and end of the pattern. (b) The eye patterns for the coupler and EDFL for the last 215 bits. The bit patterns were averaged over 300 repetitions in (a) and 18 repetitions in (b).